A cutting tool for machining a workpiece made of metals or the like comprises a holder and a cutting insert attached to the holder. The cutting edge of this cutting insert is located on the front side relative to the front surface of the holder in a direction of a holder axis and is located on the outside relative to the outer peripheral surface of the holder. With such a configuration, the cutting edge comes into contact with the workpiece and the workpiece is cut.
Patent Document 1 discloses a cutting tool having a chip pocket and a first sub-pocket. The chip pocket extends from the periphery toward the rear end side of an insert pocket. At the same time, wall surface portion having a concave-curved surface shape that configures the first sub-pocket is located on the outer peripheral surface side of the holder (4A side), where the cutting edge is located, relative to a center axis of the holder and is formed so as to be located on the upper side relative to the front of the cutting edge. In addition, the wall surface that configures the first sub-pocket is provided by being apart from the insert pocket.
With such a configuration, there is a problem in that a wider chip-discharging space may not be ensured with the first sub-pocket, causing chips to become clogged between the wall surface portion that configures the first sub-pocket and a machined wall surface if the chips flow toward the outer peripheral surface side (4A side) by becoming entangled with the rotation of the workpiece.